Afterburner igniter



Aug. 23, 1960 H. s. cRlM ETAL AFTERBURNER IGNITER 5 Sheets-Sheet 1 Filed July 28, 1959 MLM;

Aug., 23, 1960 Filed July 28, 1959 H. S. CRIM ETAL AFTERBURNER IGNITER 5 Sheets-Sheet 2 ug. 23, 195@ H. s. CHIM ETAL AFTERBURNER IGN I TE R 5 Sheets-Sheet 3 Filed July 28, 1959 w ne arme/f Aug;` 23, 1960 H. s. cRlM ETAL 2,949,738 AFTERBURNER IGNITER Filed July 28, 1959 5 Sheets-Sheet 4 5 sheets-sheet 5 Filed July 28, 1959 f77 CILV VEN TOR.

f a i n. BY MZ//aw/f /ffoaf AFTERBURNER IGNITER Filed `luly 28, 1959, Ser. No. 830,169 S Claims. (Cl. 45m-39.82)

and William W. Jacobus, by mesne assignments, to represented by the Seere- This invention relates to an aircraft propulsion unit in the form of a turbo jet provided with afterburner apparatus, and more particularly it is directed to an igniter for the afterburner.

The primary object of this invention is to provide a new and improved afterburner igniter which will inject a relatively large quantity of fuel in one shot into the combustor of a power plant so as to propagate a pilot ame from the combustor into the afterburner for ignition thereof.

It is a further object of this invention to provide an afterburner igniter which is actuated by differential pressure of afterburner and combustor fuel pressures.

It is also an object of this invention to provide novel drain means for an igniter to avoid dripping of fuel from the igniter into the combustor.

These and other objects will be readily apparent from the following description of the invention when read in conjunction with the accompanying drawings wherein:

Figure l is a schematic showing of the igniter in relation to the power plant of an aircraft;

Figure 2 is a cross-sectional View of one embodiment of the igniter in its normal or non-actuated condition;

Figure 3 is similar to Figure 1 showing the igniter actuated;

Figure 4 is a cross-sectional view showing a modification of the igniter of Figure 2 in non-actuated condition;

Figure 5 shows the igniter of Figure 3 in actuated condition.

Referring to the drawings, throughout which the same reference numerals designate the same parts, indicates a gas turbine power plant of suitable construction, generally including an open-ended casing 12, one end, 14, of which is an air intake and the other, 16, an exhaust nozzle or outlet. Axially aligned within the casing 12 is a compressor 18, combustor 20, and turbine 22, the latter being connected by a shaft 2'4 to drive the compressor. An afterburner is interposed between the turbine 22 and the outlet 16; it has the usual ring-like manifold 28 mounted transversely within the casing.

Fuel is delivered to the combustor 20 from a combustor fuel pump 36 (Fig. l) to which fuel is supplied from some source, 32. Air drawn in through the inlet 14 is compressed7 mixed with the fuel in the combustor, and ignited by an ordinary spark igniter (not shown). The resulting force produced drives the turbine 22 and provides a propulsive thrust on leaving the outlet 16. Inasmuch as the high speed gases discharged from the turbine contain considerable oxygen, additional fuel is added into the afterburner from a manifold 13 which is supplied from the fuel source 32 under pressure from an afterburner fuel pump 34 that is connected to the manifold by a conduit 36. Re-ignition of the air-fuel mixture so created is obtained by temporarily propagating a pilot flame from the combustor, through the turbine, and into the afterburner. The pilot llame is formed by injecting a denite charge of fuel from a conduit 38 connected to the afterburner fuel pump 34 through an igniter means 4t) and conduit 39 at a convenient point within the combustor or near the turbine where the gases exhausting from the combustor are sufficiently hot to be ignited without requiring a spark.

The igniter means 40 (Figs. 2 and 3) comprises, broadly, a housing or body 42 provided with a fuel squirt valve 44 in which the required quantity of fuel for forming the pilot flame is collected, a transfer or pilot valve 46 which essentially triggers the squirt valve, a shut-off valve 48 for preventing fuel flow into the igniter from the afterburner fuel pump and a differential pressure valve 5o for controlling the shut-olf Valve.

The squirt valve 44 includes a horizontal cylindrical valve bore 52 having a reciprocably moveable, cupshaped valve member or piston 54 which divides the -bore 52 into a fuel chamber 56 and a pressure chamber 58. A spring 6i) normally biases the piston to the left toward the pressure chamber 58. One or more nipples y62 on the closed end of the piston prevent it from abutting the end wall 64 of the valve bore. A fuel inlet passage 66 communicates with the fuel chamber 56 through the bottom of the peripheral wall forming the bore 52 intermediate its ends and nearthe open end of piston `54, when the piston is in a non-actuated position as shown in Fig. 2. An outlet passage 68 communicates with the bottom of the fuel chamber 56 near its fixed, right end wall 70. The pressure chamber 58 is provided with a fuel inlet passage 69 opening into it near the top of the fixed end wall 64.

The pilot valve 46 has a horizontal, cylindrical, valve bore '72 fitted with a axially reciprocable piston 74 cupped at its right end and provided with a compression spring 76 which normally urges it to the left.' Three axially spaced, annular grooves 78, -80 and 82 form four lands 84, 86, 8S and 9) on the outer surface of the pilot piston 74. An inlet conduit or passage 92 or opening in the bottom of Valve bore 72 normally communicates with the fuel chamber 56 of squirt valve 44 through groove 80 on pilot valve piston 74 and passage 66. Inlet passage 92 also communicates with inlet passage 69 to pressure chamber 58 of squirt valve 44 upon actuation of pilot valve piston 74 (Fig. 3). An inlet passage 94 having a restricting orifice 96 connects inlet passage 92 to pilot valve bore 72 through its fixed, left end wall 98. A restricted outlet passage 100 opening in the bottom 0f the bore '72 normally interconnects the fuel chamber 56 of squirt valve 44 to drain in the nozzle portion of the aircraft casing 12 by way of conduit 102, passage 104, and squirt valve outlet passage `68. A second fuel outlet passage 106 opening in the bottom of pilot valve bore 72 interconnects fuel chamber 56 in squirt valve 44 through its outlet passage `68, pilot piston groove `82, and conduit 38 to combustor 20 for injection of fuel to ignite the afterburner, upon actuation of pilot valve pist0n 74 (Fig. 3

The shut-off valve 48 has a horizontal bore 108 intersecting inlet passage 92 at right angles provided with a reciprocable valve member 110 in sliding con/tact with the top wall 112 of the bore for covering Vand uncovering the opening or port 114 into inlet passage 92. The bottom wall 116 is not contacted by piston 110' so that afterburner fuel pressure always passes axially in bore 108 from con` duit 39 leading from `afterburner fuel pump 34.

The differential pressure valve 50 has a cylindrical, horizontal bore 118 that is an enlarged, axial extension from the right hand end of shut-off valve bore 108, and has within it a reciprocable, cup-shaped piston 120 having its closed end directed toward the shut-off valve and connected to it by a rod 122. Thus, shut-off valve member 110 is capable of reciprocating with differential fuel pressure valve piston 120. A frusto conical valve seat 124 diverging `from the direction of the shut-ott valve joins the shut-` off valve bore 108 to the differential fuel pressure valve bore 118. A frusto conical surface portion 126 of suitable size is provided around the edge of the piston 120 so as to make a line sealing contact on the valve seat 124. The open end of piston 120 carries a compression spring 128 to urge it to the left and is subjected to combustor fuel pressure which enters through the end wall 130 of diferential pressure valve piston 120 from an inlet conduit 131 connected to combustor fuel pump 30.

A jacket 132 is provided around squirt valve 44 having an inlet 134 and outlet 136 connected to combustor fuel pump 30 for circulating fuel therefrom to keep valve 44 cool. There is no possibility of leakage into the squirt valve since the only way out for the fuel is through the lines 134 and 136 to the combustor fuel pump.

Passages are provided in the igniter 40 for venting the inlets and valves to the nozzle area of the power plant by way of conduit 102. Thus, conduit L138 opening in the top of fuel chamber S6 of squirt valve 44 communicates with the drainage conduit 102 yas does conduit 140 from the right end of pilot valve bore 72. Drainage from inlet passage 92 to fuel chamber 56 and restricted inlet 94 to the pilot valve drain through a concavity 115 in the upper face of the shut-olf valve member 110, when it is closed as shown in Fig. 2, into passage 142 that joins conduit 102 by Way of passage 104. Inlet 69 to the pressure chamber 58 drains through groove 78 in pilot valve piston 74 (Fig. 2) into passage 104.

In operation, when the afterburner signal is turned on, by means not shown, `afterburner pump fuel pressure enters shut-olf valve bore 108 and overcomes the pressure applied from the right to differential pressure piston 120 and translates piston 120 accordingly. As piston 120 moves from the frusto conical seat 121 a greater piston area is exposed to the afterburner pump fuel pressure thereby giving it a snap action to the right. If desired, it may be made to operate at to l0 p.s.i. before fuel is allowed to flow to the afterburner manifold by the provision of a check valve 142 designed for the purpose, in manifold line 36. On movement of differential pressure valve piston 120 to the right shut-off piston `110 uncovers pont 114 to inlet line 92 and allows -afterburner fuel to iiow through groove 80 on pilot valve piston 74, passage 66, `and into fuel chamber 56 of squirt valve 44. As chamber 456 fills, air is displaced and leaves through outlet passage 68, groove 82 of pilot valve piston 74 and through restricted outlet 100 to drain. When chamber 56 is full and fuel starts flowing through restricted outlet 100, a fuel pressure drop is felt that is transmitted back to inlet 92 and causes the afterburner fuel to pass from it through restricted inlet 94 into the left side of pilot valve bore 72. This translates pilot valve piston 74 to the right overcoming the pressure of spring 76. Inlet 92 now communicates with pressure chamber 58 through groove 80 of pilot valve piston 74 and inlet 69, allowing afterburner fuel pump pressure to be applied to the left side of squirt valve piston 54. On movement of piston 54 to the right, drainage outlet 138 and inlet 66 of fuel chamber 56 are closed by piston 54 and fuel from chamber 56 is discharged through outlet 68 around the groove 82 and through conduits 106 and 38 into the combustor. Any leakage around piston 54 would go around the annular groove 139 in the wall of squirt valve bore 52 and out line 138 to drain conduit 102; thus no fuel will dribble into the squirt line 38.

When afterburner signal is off, combustor pump fuel pressure is now applied to the left side of differential pressure valve piston 120-by way of conduit 144 from pump 32as well as to the right side-from conduit 131. Piston 120 is, therefore, returned to the left under force of spring 128 and pilot valve piston 74 under force of spring 76. Piston 54 also returns by force of spring 60 since pressure chamber 58 may not drain or vent through the pilot valve. The fuel behind the pilot valve piston also vents, by way of inlet 94 and passage 142.

The embodiment shown in Figs. 4 and 5-the same numerals are used to designate the parts that are similar to Figs. 2 and 3-differs from that of Figs. 2 and 3 in the use of the fuel pressure transmitted back from restricted orifice through fuel chamber 56 and inlet 92 for actuating the pilot valve piston 74. In this respect, the restricted fuel line 94 branching from inlet 92 for actuating pilot 'valve piston 74 (of Figs. 3 and 4) has been replaced by a passage or conduit 146 opening in the wall of the pilot valve bore 72 in the vicinity of the entrance of line 68 from fuel chamber 56, but terminating in the same left, end wall 98 for application of fuel back pressure to the pilot valve piston. A line 148 from inlet passage 69 to fthe pressure chamber 58 of the spirit valve 44 also communicates with pilot valve bore 72 through end Wall 98 through a' check valve 150, shown schematically. A drain passage 152 is provided to carry fuel back from the left side of pilot valve piston 74 through shut-off valve member and into passage 142 to drain.

1t can be seen that now when fuel from chamber 56 begins to pass through the orifice 95 in outlet 10) the pressure resistance offered by orifice 95 will cause it to be directed into line 146 through end Wall 98 and cause the pilot valve piston 74 to translate to the right. This is so, since drain line 152 is now closed by shut-olf valve member 110. As pilot valve continues to translate to the right, line 146 begins to be closed by the land 88 on the pilot valve piston, but not before the land, 8S, starts to open line 69. Fuel pressure entering line 69 through the pilot valve passes through check valve in passage 148 and thereby helps translate pilot valve piston 74 to the right. This, however, is a secondary function of line 69; its main function is to allow afterburner fuel pressure to be applied to the squirt valve piston 54 to initiate the afterburner squirt. Other than the above diiference the device of Figs. 4 and 5 functions in a like manner to that of the device of Figs. 2 and 3.

Obviously many changes are possible without departing spirit of the invention. It is, therefore, understood that scope of the invention is to be determined from the appended claims.

What is claimed is:

1. In a power plant equipped with a combustor, an afterburner, a combustor fuel pressure source, and an afterburner fuel pressure source, an afterburner igniter comprising a fuel squirt valve having a valve bore and a piston therein dividing said bore into rst and second chambers and movable by afterburner fuel pressure, a pilot valve controlling afterburner fuel pressure iiow into and from said chambers having a valve bore and a piston therein, a first inlet provided with `an inlet port normally connecting said afterburner fuel pressure source through said pilot valve to said first chamber, a restricted outlet connecting said iirst chamber through said pilot valve to drain to permit filling said rst chamber with fuel from said first inlet, a restricted conduit connecting said source of afterburner lfuel pressure through said inlet port to said pilot valve to actuate said pilot valve piston upon said first chamber being filled with fuel and to stop fuel iiow into said iirst chamber and therefrom through said restricted outlet, a normally closed second outlet connecting said lirst chamber through said pilot valve to said combuster opened upon actuation of said pilot valve piston, and a normally closed second inlet connecting said inlet port through said pilot valve to said second chamber that is opened upon actuation of said pilot valve piston, whereby said fuel squirt Valve piston is actuated to eject fuel from said first chamber through said second outlet into said combuster.

2. The device of claim 1 including means responsive to the pressure differential of afterburner fuel pressure and combuster fuel pressure for controlling fuel flow into said pilot valve. i

3. The device of claim 1 including means to drain said valves and inlets.

4. Ihe device of claim 2 wherein said means includes a shut-olf valve in said inlet port and a differential pressure valve having a piston operatively connected at one end to said shut-olf valve for opening and closing said inlet port, and said piston being subjected at said one end to said afterburner fuel pressure and at the other end to combustor fuel pressure.

5. An afterburner igniter comprising a housing, a fuel squirt valve bore in said housing and a piston therein dividing said bore into iirst and second chambers, a pilot valve bore in said housing having a piston, said housing having a fuel pressure inlet port, a rst inlet conduit connecting said port through said pilot valve piston to said rst chamber, said housing having an outlet and a restricted outlet, an outlet conduit normally connecting said first chamber through said pilot valve to said restricted outlet and adapted for communication with said outlet with movement of said pilot valve piston, a restricted conduit connecting said first inlet conduit to said pilot valve bore for actuating said piston therein, and a normally closed second inlet conduit connecting said first inlet conduit from said pilot valve piston to said second chamber upon actuation of said latter piston so as to actuate the piston in said squirt valve bore land eject fuel from said iirst chamber through said outlet.

6. The device of claim 4 including means in said housing port for opening and closing said rst inlet conduit from said port.

7. The device of claim 5 wherein said means includes a shut-off valve in said first inlet conduit a dierential pressure valve bore communicating therewith and having a piston therein, means connecting one end of said latter piston with said shut-olf valve, and inlet means for subjecting the other end of said piston in said dilferential pressure valve bore to a second pressure.

8. An afterburner igniter comprising a housing, a fuel squirt valve bore in said housing and a piston therein dividing said bore into first and second chambers, a pilot valve bore in said housing having a piston normally in a rst position and movable to a second position, said housing having a fuel pressure inlet port, a rst inlet conduit connecting said port through said pilot valve piston to said iirst chamber, said housing having an outlet and -a restricted outlet, said pilot valve piston having an annular peripheral groove, an outlet conduit normally connecting said iirst chamber through said -annular peripheral groove on said pilot valve piston to said restricted outlet and adapted for communication with said outlet with movemen of said pilot valve piston to said second position a pilot valve inlet conduit normally connecting said outlet conduit from said first chamber through said annular peripheral groove on said pilot valve piston to one end of said pilot valve bore in order to move said piston to said second inlet conduit connecting said rst inlet conduit from said pilot valve piston to said second chamber upon actuation of said latter piston so as to actuate the piston in said squirt valve bore and eject fuel from said chamber through said outlet.

References Cited in the iile of this patent UNITED STATES PATENTS 1,260,091 Stubbletield Mar. 19, 1918 2,714,803 Abild n Aug. 9, 1955 2,808,699 Ivens Oct. 8, 1957 2,913,875 Meyer Nov. 24, 1959 

